"Garrison Guard" Co. G, 24th Alabama Regt. The name of this company was "Gulf City Guards No. 2". What was the "Garrison Guard"?

Records for Captain A. Hurtel of Company G, 24th Alabama indicate that he was detached for Guard Duty at Atlanta by General Bragg in late January 1863, and assigned by Hood in late '64 to command the military prison at Macon. Ga.

Perhaps that is where the name "Garrison Guard" was derived?